1. Field of the Invention
The present invention relates to a waste toner collecting apparatus for collecting waste toner used in an electronic photography type copying machine, a printer or the like adapted to produce a color image by laying toner images of a plurality of different colors one on the other. This invention also relates to an image forming apparatus.
2. Description of the Related Art
A cleaning apparatus is normally operated to remove toner remaining on a photosensitive member of an image forming apparatus such as a copying machine or a printer after the end of an image transfer process. The toner removed from the photosensitive member is collected in a waste toner box as waste toner. When the waste toner box becomes full, it is replaced by a new one.
Tandem type image forming apparatus have been marketed in recent years. A plurality of image forming units, each having a photosensitive member, are arranged in parallel in a tandem type image forming apparatus and the toner images of different colors formed on the respective photosensitive members are transferred onto a single sheet of paper and laid one on the other to produce a color image. Residual toner is remained from each of the photosensitive members of such a tandem type image forming apparatus. When a transfer medium such as an intermediate transfer belt is employed, residual toner is remained also on the transfer medium.
When the residual toner from the plurality of photosensitive members and on the transfer medium is collected into a single waste toner box extending in the direction of arrangement of the photosensitive members, a heap of accumulated waste toner is formed in the waste toner box for each of the photosensitive members and the transfer medium. To cope with this problem, apparatus have been proposed for leveling down the heaps of waste toner accumulated in the waste toner box by means of an auger so as to increase the quantity of waste toner that can be contained in the waste toner box. For example, Jpn. Pat. Publication (Kokai) No. 2002-148884 discloses such an apparatus. Apparatus have also been proposed for detecting the volume of developer in the development unit and controls the number of rotations of the paddles for drawing up developer onto the development rollers of the development unit. For example, Jpn. Pat. Publication (Kokai) No. 8-36294 discloses such an apparatus.
However, the former known apparatus do not pay attention to the control of the auger. In other words, the auger or some other leveling member is driven to operate simply when the number of sheets where images are formed gets to a predetermined value. If images are formed with a low image density, it may be not necessary to level down the waste toner in the waste toner box when the number of image-bearing sheets gets to a predetermined value.
Generally, the number of rotation of the leveling member is designed to operate on an assumption that images are formed with a high image density and waste toner is defecated at a relatively high rate from the viewpoint of preventing a waste toner collecting mechanism from being broken down and improving the safety of the mechanism. In other words, the leveling member is driven to operate frequently on an assumption that waste toner is defecated at a relatively high rate. When the leveling member is driven to rotate frequently, so much flying toner is occurred in the waste toner box.
On the other hand, in the case of apparatus adapted to detect a full condition of the waste toner box typically by means of an optical sensor, the full condition detecting section of the apparatus can erroneously detect a full condition in the waste toner box when it is stained by flying toner.
Thus, there is a demand for an arrangement for satisfactorily leveling waste toner in a waste toner box and efficiently collecting waste toner, while minimizing flying toner in the waste toner box in order to prevent the full condition detecting section from detecting a full condition in error due to the smudge thereof given by flying toner when the waste toner defecated from a plurality of image forming units and a transfer medium is collected in the single waste toner box.